The proposal seeks to enhance the capacity of California to use existing state-level workers' compensation (WC) data to conduct public health surveillance including 1) collection, analysis, interpretation, use, and dissemination of findings on the incidence of occupational injuries, illnesses, deaths and exposures to hazards; 2) identification of trends, emerging issues, high-risk industries and worker populations; and 3) development of recommendations for workplace interventions. Our specific aims include: 1. Combine California Workers Compensation Information System (WCIS) claims data with Quarterly Census of Employment and Wages and other denominator sources, including the American Community Survey, to develop rates of WC claims per full time equivalent (FTE) by NAICS industries and employer sizes, including sensitivity analyses among rate estimates from various denominator data sources. 2. Distribute a data analysis report for the public that includes rates of WC claims by 1) medical-only and lost- time claims; 2) NIOSH NORA industry sectors, NAICS industries, employer size categories; and 3) injury/illness part of body, nature, and cause. 3. Summarize the utility and limitations of California's WCIS and denominator databases. 4. Create a publically accessible de-identified WC case dataset including First Report of Injury (FROI) fields, and coordinate with NIOSH an assessment of California WC costs. California WC claim rates will be calculated by matching each year's WCIS claims to an establishment in the QCEW database by establishment FEIN, summing claims and denominators by NAICS industry codes and establishment size, and matching NAICS employee denominator with hours worked per week and weeks worked per year from ACS by NAICS industry. A surveillance system evaluation will include sensitivity analyses and cost calculations, and summarize technical information about the databases. California's WC system is the largest in the country. As a non-exclusive WC fund state with medical billing data, WCIS provides a rich data source for increased occupational injury and illness surveillance. California has an established research unit at DIR that is a well-integrated part of the labor agency, and CDPH and DIR have a history of collaborating to use data to augment policy changes including important health and safety regulations, including WC regulations related to opioid use, back surgery, and CTS. Adding industry rates increases our capacity to implement new worker protections and interventions and expands the use of WC for surveillance purposes.